I doubt anybody whould like to use a shareware mp3 player with a banner on it. Even a freeware player doesn’t make any sense for me, because there are Windows Media Player, WinAmp, foobar and so on out there. BTW, 99% of such an app whould be FMOD and only 1% or less whould be your own code. Why not developing something really useful first and then trying to earn money selling it?